But much of those gains were fueled by H-P, which went from being the Dow’s biggest laggard in 2012 to its top performer this year.

It’s unclear whether Tuesday’s developments would change much for traditional “dogs” investors. The strategy effectively calls for an investor to buy a certain basket of stocks on Jan. 1 and hold them through the end of the year. But different variations and interpretations of this investing theme have developed throughout the years and could be impacted by H-P leaving the Dow.

For answers, MoneyBeat tossed a call to money manager Michael O’Higgins, who is credited with creating the Dogs approach in the early 1990s. He suggested “dog” investors shouldn’t change their approach based on Tuesday’s announcement. Investing in the dogs is “a once-a-year thing,” Mr. O’Higgins said. “No reason to change at this point.”